1. Field of the Invention
The present invention relates to a dustproof structure of an optical box in which a latent image is formed by effecting scan and exposure on a photosensitive material using a laser beam.
2. Description of the Related Art
In recent years, an image exposure apparatus, in which a photographic printing paper is scanned and exposed using a light source which emits a laser beam, has been widely used in writing in a digital laboratory system for recording, on a photographic printing paper, an image recorded on a photographic film.
Such an image exposure apparatus includes light sources which respectively emit laser beams of red (R), green (G), and blue (B), and based on color image data, modulates the laser beam for each of the colors of R, G, and B. The laser beam is deflected by a deflecting device such as a polygon mirror in a main scan direction, and the photographic printing paper is conveyed in a sub-scan direction. The photographic printing paper is thus scanned and exposed with the laser beam via an optical system comprised of an fxcex8 lens, a cylindrical lens, a plane mirror, a reflexing mirror, and the like, and a color image is recorded on the photographic printing paper.
In a scanning optical system used in the above-described image exposure apparatus, as shown in FIG. 10, a deflecting device such as a polygon mirror 250, and an optical system 252 are disposed within an optical box 254 so as to prevent dust and the like from adhering thereto. An exit window 256 is formed on a side surface 254A of the optical box 254 and a laser beam is transmitted through the exit window 256. Further, a duct 258 is provided in the vicinity of the exit window 256 and includes a fan 260. During scan and exposure, air flow is supplied into the duct 258 by the fan 260 so as to prevent dust from adhering to the exit window 256 and the like.
However, the above-described dustproof structure can prevent dust from adhering to the exit window, but cannot prevent dust from adhering to the deflecting device such as a polygon mirror, and the optical system, which are disposed within the optical box. In order to prevent deterioration in the image quality of a photographic printing paper or the like, it is necessary to prevent dust from directly adhering to the deflecting device, the optical system, and the like.
Accordingly, an object of the present invention is to provide a dustproof structure of an optical box, which can prevent intrusion of dust into the optical box.
In accordance with a first aspect of the present invention, there is provided a dustproof structure of an optical box, which is used in an optical box which includes a polygon section comprised of deflecting means for deflecting laser beams and an optical system by which laser beams deflected by the deflecting means are converged on a photosensitive material, the dustproof structure of an optical box comprising: an opening formed in the optical box for guiding the laser beams to the photosensitive material; and pressurizing means for pressurizing an interior of the optical box by supplying air to the interior of the optical box, thereby preventing intrusion of dust from the opening and from outside of the optical box.
According to the above-described structure, during the scan and exposure, the laser beams are deflected by the deflecting means. The laser beams deflected by the deflecting means are transmitted through the optical system and emitted from the opening. Thereafter, the laser beams are converged on the photosensitive material.
In this case, air is supplied into the optical box by the pressurizing means so that the interior of the optical box is pressurized. For this reason, intrusion of dust from the opening and from the outside of the optical box can be prevented. As a result, no dust adheres to the deflecting means and the optical system and the respective functions thereof can be maintained.
In accordance with a second aspect of the present invention, there is provided a dustproof structure of an optical box according to the first aspect which further comprises: opening and closing means for opening and closing the opening; and control means in which, when scan and exposure is being carried out by the laser beams, the opening is opened by the opening and closing means, and thereafter, the interior of the optical box is pressurized by the pressurizing means, and when the scan and exposure ends, the pressurizing means is stopped, and thereafter, the opening is closed by the opening and closing means.
According to the above-described structure, it is necessary to prevent the intrusion of dust from the opening into the optical box, and therefore, the opening and closing means is provided in the opening. The opening is closed by the opening and closing means in a normal state (in a state of no scan and exposure being effected).
In order for the laser beams to be guided to the photosensitive material when the photosensitive material is scanned and exposed by the laser beams, the opening is placed in an open state by the opening and closing means. Thereafter, the pressurizing means is controlled by the control means so that the interior of the optical box is pressurized.
When the scan and exposure of the photosensitive material by the laser beams is completed, the pressurizing means is controlled by the control means to stop pressurization, and thereafter, the opening is placed in a closed state by the opening and closing means.
As described above, during the scan and exposure, the opening is opened by the opening and closing means, and thereafter, the interior of the optical box is pressurized. When the scan and exposure is completed, the opening is controlled so as to be closed after the pressurization has been stopped. As a result, the interior of the optical box is pressurized with the opening being placed in a constantly open state, and therefore, it is possible to prevent dust and the like adhering to the inner side of the opening and closing means from spreading within the optical box.
Further, in accordance with a third aspect of the present invention, there is provided a dustproof structure of an optical box according to the first aspect, in which a light source section which emits the laser beams, the polygon section, and an exit section which emits the laser beams emitted from the polygon section outside the optical box are provided in such a manner that differences in the degree of sealing are made among chambers in which the three sections are disposed by partitioning.
According to the above-described structure, the light source section, the polygon section, and the exit section are disposed by partitioning in the respective corresponding chambers. As a result, differences in the degree of sealing between these chambers are made.
In this case, generally, a high-level sealing degree is required by the polygon section, a medium-level sealing degree is required by the exit section, and a low-level of sealing degree is required by the light source section. Accordingly, by making differences in the degree of sealing between these chambers, the above-described requirements can be satisfied.